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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import static com.google.common.base.Preconditions.checkState;<a name="line.21"></a>
<span class="sourceLineNo">022</span><a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.annotations.Beta;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.annotations.GwtCompatible;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.annotations.GwtIncompatible;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.base.Function;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import com.google.common.base.Joiner;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import com.google.common.base.Objects;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import com.google.common.base.Optional;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import com.google.common.base.Preconditions;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import com.google.common.base.Predicate;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import com.google.common.base.Predicates;<a name="line.32"></a>
<span class="sourceLineNo">033</span><a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.Arrays;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.Collection;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.Collections;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.Comparator;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.Enumeration;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.Iterator;<a name="line.39"></a>
<span class="sourceLineNo">040</span>import java.util.List;<a name="line.40"></a>
<span class="sourceLineNo">041</span>import java.util.ListIterator;<a name="line.41"></a>
<span class="sourceLineNo">042</span>import java.util.NoSuchElementException;<a name="line.42"></a>
<span class="sourceLineNo">043</span>import java.util.PriorityQueue;<a name="line.43"></a>
<span class="sourceLineNo">044</span>import java.util.Queue;<a name="line.44"></a>
<span class="sourceLineNo">045</span><a name="line.45"></a>
<span class="sourceLineNo">046</span>import javax.annotation.Nullable;<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span>/**<a name="line.48"></a>
<span class="sourceLineNo">049</span> * This class contains static utility methods that operate on or return objects<a name="line.49"></a>
<span class="sourceLineNo">050</span> * of type {@link Iterator}. Except as noted, each method has a corresponding<a name="line.50"></a>
<span class="sourceLineNo">051</span> * {@link Iterable}-based method in the {@link Iterables} class.<a name="line.51"></a>
<span class="sourceLineNo">052</span> *<a name="line.52"></a>
<span class="sourceLineNo">053</span> * &lt;p&gt;&lt;i&gt;Performance notes:&lt;/i&gt; Unless otherwise noted, all of the iterators<a name="line.53"></a>
<span class="sourceLineNo">054</span> * produced in this class are &lt;i&gt;lazy&lt;/i&gt;, which means that they only advance<a name="line.54"></a>
<span class="sourceLineNo">055</span> * the backing iteration when absolutely necessary.<a name="line.55"></a>
<span class="sourceLineNo">056</span> *<a name="line.56"></a>
<span class="sourceLineNo">057</span> * &lt;p&gt;See the Guava User Guide section on &lt;a href=<a name="line.57"></a>
<span class="sourceLineNo">058</span> * "http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained#Iterables"&gt;<a name="line.58"></a>
<span class="sourceLineNo">059</span> * {@code Iterators}&lt;/a&gt;.<a name="line.59"></a>
<span class="sourceLineNo">060</span> *<a name="line.60"></a>
<span class="sourceLineNo">061</span> * @author Kevin Bourrillion<a name="line.61"></a>
<span class="sourceLineNo">062</span> * @author Jared Levy<a name="line.62"></a>
<span class="sourceLineNo">063</span> * @since 2.0 (imported from Google Collections Library)<a name="line.63"></a>
<span class="sourceLineNo">064</span> */<a name="line.64"></a>
<span class="sourceLineNo">065</span>@GwtCompatible(emulated = true)<a name="line.65"></a>
<span class="sourceLineNo">066</span>public final class Iterators {<a name="line.66"></a>
<span class="sourceLineNo">067</span>  private Iterators() {}<a name="line.67"></a>
<span class="sourceLineNo">068</span><a name="line.68"></a>
<span class="sourceLineNo">069</span>  static final UnmodifiableListIterator&lt;Object&gt; EMPTY_LIST_ITERATOR<a name="line.69"></a>
<span class="sourceLineNo">070</span>      = new UnmodifiableListIterator&lt;Object&gt;() {<a name="line.70"></a>
<span class="sourceLineNo">071</span>        @Override<a name="line.71"></a>
<span class="sourceLineNo">072</span>        public boolean hasNext() {<a name="line.72"></a>
<span class="sourceLineNo">073</span>          return false;<a name="line.73"></a>
<span class="sourceLineNo">074</span>        }<a name="line.74"></a>
<span class="sourceLineNo">075</span>        @Override<a name="line.75"></a>
<span class="sourceLineNo">076</span>        public Object next() {<a name="line.76"></a>
<span class="sourceLineNo">077</span>          throw new NoSuchElementException();<a name="line.77"></a>
<span class="sourceLineNo">078</span>        }<a name="line.78"></a>
<span class="sourceLineNo">079</span>        @Override<a name="line.79"></a>
<span class="sourceLineNo">080</span>        public boolean hasPrevious() {<a name="line.80"></a>
<span class="sourceLineNo">081</span>          return false;<a name="line.81"></a>
<span class="sourceLineNo">082</span>        }<a name="line.82"></a>
<span class="sourceLineNo">083</span>        @Override<a name="line.83"></a>
<span class="sourceLineNo">084</span>        public Object previous() {<a name="line.84"></a>
<span class="sourceLineNo">085</span>          throw new NoSuchElementException();<a name="line.85"></a>
<span class="sourceLineNo">086</span>        }<a name="line.86"></a>
<span class="sourceLineNo">087</span>        @Override<a name="line.87"></a>
<span class="sourceLineNo">088</span>        public int nextIndex() {<a name="line.88"></a>
<span class="sourceLineNo">089</span>          return 0;<a name="line.89"></a>
<span class="sourceLineNo">090</span>        }<a name="line.90"></a>
<span class="sourceLineNo">091</span>        @Override<a name="line.91"></a>
<span class="sourceLineNo">092</span>        public int previousIndex() {<a name="line.92"></a>
<span class="sourceLineNo">093</span>          return -1;<a name="line.93"></a>
<span class="sourceLineNo">094</span>        }<a name="line.94"></a>
<span class="sourceLineNo">095</span>      };<a name="line.95"></a>
<span class="sourceLineNo">096</span><a name="line.96"></a>
<span class="sourceLineNo">097</span>  /**<a name="line.97"></a>
<span class="sourceLineNo">098</span>   * Returns the empty iterator.<a name="line.98"></a>
<span class="sourceLineNo">099</span>   *<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * &lt;p&gt;The {@link Iterable} equivalent of this method is {@link<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * ImmutableSet#of()}.<a name="line.101"></a>
<span class="sourceLineNo">102</span>   */<a name="line.102"></a>
<span class="sourceLineNo">103</span>  public static &lt;T&gt; UnmodifiableIterator&lt;T&gt; emptyIterator() {<a name="line.103"></a>
<span class="sourceLineNo">104</span>    return emptyListIterator();<a name="line.104"></a>
<span class="sourceLineNo">105</span>  }<a name="line.105"></a>
<span class="sourceLineNo">106</span><a name="line.106"></a>
<span class="sourceLineNo">107</span>  /**<a name="line.107"></a>
<span class="sourceLineNo">108</span>   * Returns the empty iterator.<a name="line.108"></a>
<span class="sourceLineNo">109</span>   *<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * &lt;p&gt;The {@link Iterable} equivalent of this method is {@link<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * ImmutableSet#of()}.<a name="line.111"></a>
<span class="sourceLineNo">112</span>   */<a name="line.112"></a>
<span class="sourceLineNo">113</span>  // Casting to any type is safe since there are no actual elements.<a name="line.113"></a>
<span class="sourceLineNo">114</span>  @SuppressWarnings("unchecked")<a name="line.114"></a>
<span class="sourceLineNo">115</span>  static &lt;T&gt; UnmodifiableListIterator&lt;T&gt; emptyListIterator() {<a name="line.115"></a>
<span class="sourceLineNo">116</span>    return (UnmodifiableListIterator&lt;T&gt;) EMPTY_LIST_ITERATOR;<a name="line.116"></a>
<span class="sourceLineNo">117</span>  }<a name="line.117"></a>
<span class="sourceLineNo">118</span><a name="line.118"></a>
<span class="sourceLineNo">119</span>  private static final Iterator&lt;Object&gt; EMPTY_MODIFIABLE_ITERATOR =<a name="line.119"></a>
<span class="sourceLineNo">120</span>      new Iterator&lt;Object&gt;() {<a name="line.120"></a>
<span class="sourceLineNo">121</span>        @Override public boolean hasNext() {<a name="line.121"></a>
<span class="sourceLineNo">122</span>          return false;<a name="line.122"></a>
<span class="sourceLineNo">123</span>        }<a name="line.123"></a>
<span class="sourceLineNo">124</span><a name="line.124"></a>
<span class="sourceLineNo">125</span>        @Override public Object next() {<a name="line.125"></a>
<span class="sourceLineNo">126</span>          throw new NoSuchElementException();<a name="line.126"></a>
<span class="sourceLineNo">127</span>        }<a name="line.127"></a>
<span class="sourceLineNo">128</span><a name="line.128"></a>
<span class="sourceLineNo">129</span>        @Override public void remove() {<a name="line.129"></a>
<span class="sourceLineNo">130</span>          throw new IllegalStateException();<a name="line.130"></a>
<span class="sourceLineNo">131</span>        }<a name="line.131"></a>
<span class="sourceLineNo">132</span>      };<a name="line.132"></a>
<span class="sourceLineNo">133</span><a name="line.133"></a>
<span class="sourceLineNo">134</span>  /**<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * Returns the empty {@code Iterator} that throws<a name="line.135"></a>
<span class="sourceLineNo">136</span>   * {@link IllegalStateException} instead of<a name="line.136"></a>
<span class="sourceLineNo">137</span>   * {@link UnsupportedOperationException} on a call to<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * {@link Iterator#remove()}.<a name="line.138"></a>
<span class="sourceLineNo">139</span>   */<a name="line.139"></a>
<span class="sourceLineNo">140</span>  // Casting to any type is safe since there are no actual elements.<a name="line.140"></a>
<span class="sourceLineNo">141</span>  @SuppressWarnings("unchecked")<a name="line.141"></a>
<span class="sourceLineNo">142</span>  static &lt;T&gt; Iterator&lt;T&gt; emptyModifiableIterator() {<a name="line.142"></a>
<span class="sourceLineNo">143</span>    return (Iterator&lt;T&gt;) EMPTY_MODIFIABLE_ITERATOR;<a name="line.143"></a>
<span class="sourceLineNo">144</span>  }<a name="line.144"></a>
<span class="sourceLineNo">145</span><a name="line.145"></a>
<span class="sourceLineNo">146</span>  /** Returns an unmodifiable view of {@code iterator}. */<a name="line.146"></a>
<span class="sourceLineNo">147</span>  public static &lt;T&gt; UnmodifiableIterator&lt;T&gt; unmodifiableIterator(<a name="line.147"></a>
<span class="sourceLineNo">148</span>      final Iterator&lt;T&gt; iterator) {<a name="line.148"></a>
<span class="sourceLineNo">149</span>    checkNotNull(iterator);<a name="line.149"></a>
<span class="sourceLineNo">150</span>    if (iterator instanceof UnmodifiableIterator) {<a name="line.150"></a>
<span class="sourceLineNo">151</span>      return (UnmodifiableIterator&lt;T&gt;) iterator;<a name="line.151"></a>
<span class="sourceLineNo">152</span>    }<a name="line.152"></a>
<span class="sourceLineNo">153</span>    return new UnmodifiableIterator&lt;T&gt;() {<a name="line.153"></a>
<span class="sourceLineNo">154</span>      @Override<a name="line.154"></a>
<span class="sourceLineNo">155</span>      public boolean hasNext() {<a name="line.155"></a>
<span class="sourceLineNo">156</span>        return iterator.hasNext();<a name="line.156"></a>
<span class="sourceLineNo">157</span>      }<a name="line.157"></a>
<span class="sourceLineNo">158</span>      @Override<a name="line.158"></a>
<span class="sourceLineNo">159</span>      public T next() {<a name="line.159"></a>
<span class="sourceLineNo">160</span>        return iterator.next();<a name="line.160"></a>
<span class="sourceLineNo">161</span>      }<a name="line.161"></a>
<span class="sourceLineNo">162</span>    };<a name="line.162"></a>
<span class="sourceLineNo">163</span>  }<a name="line.163"></a>
<span class="sourceLineNo">164</span><a name="line.164"></a>
<span class="sourceLineNo">165</span>  /**<a name="line.165"></a>
<span class="sourceLineNo">166</span>   * Simply returns its argument.<a name="line.166"></a>
<span class="sourceLineNo">167</span>   *<a name="line.167"></a>
<span class="sourceLineNo">168</span>   * @deprecated no need to use this<a name="line.168"></a>
<span class="sourceLineNo">169</span>   * @since 10.0<a name="line.169"></a>
<span class="sourceLineNo">170</span>   */<a name="line.170"></a>
<span class="sourceLineNo">171</span>  @Deprecated public static &lt;T&gt; UnmodifiableIterator&lt;T&gt; unmodifiableIterator(<a name="line.171"></a>
<span class="sourceLineNo">172</span>      UnmodifiableIterator&lt;T&gt; iterator) {<a name="line.172"></a>
<span class="sourceLineNo">173</span>    return checkNotNull(iterator);<a name="line.173"></a>
<span class="sourceLineNo">174</span>  }<a name="line.174"></a>
<span class="sourceLineNo">175</span><a name="line.175"></a>
<span class="sourceLineNo">176</span>  /**<a name="line.176"></a>
<span class="sourceLineNo">177</span>   * Returns the number of elements remaining in {@code iterator}. The iterator<a name="line.177"></a>
<span class="sourceLineNo">178</span>   * will be left exhausted: its {@code hasNext()} method will return<a name="line.178"></a>
<span class="sourceLineNo">179</span>   * {@code false}.<a name="line.179"></a>
<span class="sourceLineNo">180</span>   */<a name="line.180"></a>
<span class="sourceLineNo">181</span>  public static int size(Iterator&lt;?&gt; iterator) {<a name="line.181"></a>
<span class="sourceLineNo">182</span>    int count = 0;<a name="line.182"></a>
<span class="sourceLineNo">183</span>    while (iterator.hasNext()) {<a name="line.183"></a>
<span class="sourceLineNo">184</span>      iterator.next();<a name="line.184"></a>
<span class="sourceLineNo">185</span>      count++;<a name="line.185"></a>
<span class="sourceLineNo">186</span>    }<a name="line.186"></a>
<span class="sourceLineNo">187</span>    return count;<a name="line.187"></a>
<span class="sourceLineNo">188</span>  }<a name="line.188"></a>
<span class="sourceLineNo">189</span><a name="line.189"></a>
<span class="sourceLineNo">190</span>  /**<a name="line.190"></a>
<span class="sourceLineNo">191</span>   * Returns {@code true} if {@code iterator} contains {@code element}.<a name="line.191"></a>
<span class="sourceLineNo">192</span>   */<a name="line.192"></a>
<span class="sourceLineNo">193</span>  public static boolean contains(Iterator&lt;?&gt; iterator, @Nullable Object element)<a name="line.193"></a>
<span class="sourceLineNo">194</span>  {<a name="line.194"></a>
<span class="sourceLineNo">195</span>    if (element == null) {<a name="line.195"></a>
<span class="sourceLineNo">196</span>      while (iterator.hasNext()) {<a name="line.196"></a>
<span class="sourceLineNo">197</span>        if (iterator.next() == null) {<a name="line.197"></a>
<span class="sourceLineNo">198</span>          return true;<a name="line.198"></a>
<span class="sourceLineNo">199</span>        }<a name="line.199"></a>
<span class="sourceLineNo">200</span>      }<a name="line.200"></a>
<span class="sourceLineNo">201</span>    } else {<a name="line.201"></a>
<span class="sourceLineNo">202</span>      while (iterator.hasNext()) {<a name="line.202"></a>
<span class="sourceLineNo">203</span>        if (element.equals(iterator.next())) {<a name="line.203"></a>
<span class="sourceLineNo">204</span>          return true;<a name="line.204"></a>
<span class="sourceLineNo">205</span>        }<a name="line.205"></a>
<span class="sourceLineNo">206</span>      }<a name="line.206"></a>
<span class="sourceLineNo">207</span>    }<a name="line.207"></a>
<span class="sourceLineNo">208</span>    return false;<a name="line.208"></a>
<span class="sourceLineNo">209</span>  }<a name="line.209"></a>
<span class="sourceLineNo">210</span><a name="line.210"></a>
<span class="sourceLineNo">211</span>  /**<a name="line.211"></a>
<span class="sourceLineNo">212</span>   * Traverses an iterator and removes every element that belongs to the<a name="line.212"></a>
<span class="sourceLineNo">213</span>   * provided collection. The iterator will be left exhausted: its<a name="line.213"></a>
<span class="sourceLineNo">214</span>   * {@code hasNext()} method will return {@code false}.<a name="line.214"></a>
<span class="sourceLineNo">215</span>   *<a name="line.215"></a>
<span class="sourceLineNo">216</span>   * @param removeFrom the iterator to (potentially) remove elements from<a name="line.216"></a>
<span class="sourceLineNo">217</span>   * @param elementsToRemove the elements to remove<a name="line.217"></a>
<span class="sourceLineNo">218</span>   * @return {@code true} if any element was removed from {@code iterator}<a name="line.218"></a>
<span class="sourceLineNo">219</span>   */<a name="line.219"></a>
<span class="sourceLineNo">220</span>  public static boolean removeAll(<a name="line.220"></a>
<span class="sourceLineNo">221</span>      Iterator&lt;?&gt; removeFrom, Collection&lt;?&gt; elementsToRemove) {<a name="line.221"></a>
<span class="sourceLineNo">222</span>    checkNotNull(elementsToRemove);<a name="line.222"></a>
<span class="sourceLineNo">223</span>    boolean modified = false;<a name="line.223"></a>
<span class="sourceLineNo">224</span>    while (removeFrom.hasNext()) {<a name="line.224"></a>
<span class="sourceLineNo">225</span>      if (elementsToRemove.contains(removeFrom.next())) {<a name="line.225"></a>
<span class="sourceLineNo">226</span>        removeFrom.remove();<a name="line.226"></a>
<span class="sourceLineNo">227</span>        modified = true;<a name="line.227"></a>
<span class="sourceLineNo">228</span>      }<a name="line.228"></a>
<span class="sourceLineNo">229</span>    }<a name="line.229"></a>
<span class="sourceLineNo">230</span>    return modified;<a name="line.230"></a>
<span class="sourceLineNo">231</span>  }<a name="line.231"></a>
<span class="sourceLineNo">232</span><a name="line.232"></a>
<span class="sourceLineNo">233</span>  /**<a name="line.233"></a>
<span class="sourceLineNo">234</span>   * Removes every element that satisfies the provided predicate from the<a name="line.234"></a>
<span class="sourceLineNo">235</span>   * iterator. The iterator will be left exhausted: its {@code hasNext()}<a name="line.235"></a>
<span class="sourceLineNo">236</span>   * method will return {@code false}.<a name="line.236"></a>
<span class="sourceLineNo">237</span>   *<a name="line.237"></a>
<span class="sourceLineNo">238</span>   * @param removeFrom the iterator to (potentially) remove elements from<a name="line.238"></a>
<span class="sourceLineNo">239</span>   * @param predicate a predicate that determines whether an element should<a name="line.239"></a>
<span class="sourceLineNo">240</span>   *     be removed<a name="line.240"></a>
<span class="sourceLineNo">241</span>   * @return {@code true} if any elements were removed from the iterator<a name="line.241"></a>
<span class="sourceLineNo">242</span>   * @since 2.0<a name="line.242"></a>
<span class="sourceLineNo">243</span>   */<a name="line.243"></a>
<span class="sourceLineNo">244</span>  public static &lt;T&gt; boolean removeIf(<a name="line.244"></a>
<span class="sourceLineNo">245</span>      Iterator&lt;T&gt; removeFrom, Predicate&lt;? super T&gt; predicate) {<a name="line.245"></a>
<span class="sourceLineNo">246</span>    checkNotNull(predicate);<a name="line.246"></a>
<span class="sourceLineNo">247</span>    boolean modified = false;<a name="line.247"></a>
<span class="sourceLineNo">248</span>    while (removeFrom.hasNext()) {<a name="line.248"></a>
<span class="sourceLineNo">249</span>      if (predicate.apply(removeFrom.next())) {<a name="line.249"></a>
<span class="sourceLineNo">250</span>        removeFrom.remove();<a name="line.250"></a>
<span class="sourceLineNo">251</span>        modified = true;<a name="line.251"></a>
<span class="sourceLineNo">252</span>      }<a name="line.252"></a>
<span class="sourceLineNo">253</span>    }<a name="line.253"></a>
<span class="sourceLineNo">254</span>    return modified;<a name="line.254"></a>
<span class="sourceLineNo">255</span>  }<a name="line.255"></a>
<span class="sourceLineNo">256</span><a name="line.256"></a>
<span class="sourceLineNo">257</span>  /**<a name="line.257"></a>
<span class="sourceLineNo">258</span>   * Traverses an iterator and removes every element that does not belong to the<a name="line.258"></a>
<span class="sourceLineNo">259</span>   * provided collection. The iterator will be left exhausted: its<a name="line.259"></a>
<span class="sourceLineNo">260</span>   * {@code hasNext()} method will return {@code false}.<a name="line.260"></a>
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<span class="sourceLineNo">262</span>   * @param removeFrom the iterator to (potentially) remove elements from<a name="line.262"></a>
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<span class="sourceLineNo">280</span>   * Determines whether two iterators contain equal elements in the same order.<a name="line.280"></a>
<span class="sourceLineNo">281</span>   * More specifically, this method returns {@code true} if {@code iterator1}<a name="line.281"></a>
<span class="sourceLineNo">282</span>   * and {@code iterator2} contain the same number of elements and every element<a name="line.282"></a>
<span class="sourceLineNo">283</span>   * of {@code iterator1} is equal to the corresponding element of<a name="line.283"></a>
<span class="sourceLineNo">284</span>   * {@code iterator2}.<a name="line.284"></a>
<span class="sourceLineNo">285</span>   *<a name="line.285"></a>
<span class="sourceLineNo">286</span>   * &lt;p&gt;Note that this will modify the supplied iterators, since they will have<a name="line.286"></a>
<span class="sourceLineNo">287</span>   * been advanced some number of elements forward.<a name="line.287"></a>
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<span class="sourceLineNo">305</span>   * Returns a string representation of {@code iterator}, with the format<a name="line.305"></a>
<span class="sourceLineNo">306</span>   * {@code [e1, e2, ..., en]}. The iterator will be left exhausted: its<a name="line.306"></a>
<span class="sourceLineNo">307</span>   * {@code hasNext()} method will return {@code false}.<a name="line.307"></a>
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<span class="sourceLineNo">317</span>  /**<a name="line.317"></a>
<span class="sourceLineNo">318</span>   * Returns the single element contained in {@code iterator}.<a name="line.318"></a>
<span class="sourceLineNo">319</span>   *<a name="line.319"></a>
<span class="sourceLineNo">320</span>   * @throws NoSuchElementException if the iterator is empty<a name="line.320"></a>
<span class="sourceLineNo">321</span>   * @throws IllegalArgumentException if the iterator contains multiple<a name="line.321"></a>
<span class="sourceLineNo">322</span>   *     elements.  The state of the iterator is unspecified.<a name="line.322"></a>
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<span class="sourceLineNo">344</span>   * Returns the single element contained in {@code iterator}, or {@code<a name="line.344"></a>
<span class="sourceLineNo">345</span>   * defaultValue} if the iterator is empty.<a name="line.345"></a>
<span class="sourceLineNo">346</span>   *<a name="line.346"></a>
<span class="sourceLineNo">347</span>   * @throws IllegalArgumentException if the iterator contains multiple<a name="line.347"></a>
<span class="sourceLineNo">348</span>   *     elements.  The state of the iterator is unspecified.<a name="line.348"></a>
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<span class="sourceLineNo">351</span>  public static &lt;T&gt; T getOnlyElement(Iterator&lt;? extends T&gt; iterator, @Nullable T defaultValue) {<a name="line.351"></a>
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<span class="sourceLineNo">355</span>  /**<a name="line.355"></a>
<span class="sourceLineNo">356</span>   * Copies an iterator's elements into an array. The iterator will be left<a name="line.356"></a>
<span class="sourceLineNo">357</span>   * exhausted: its {@code hasNext()} method will return {@code false}.<a name="line.357"></a>
<span class="sourceLineNo">358</span>   *<a name="line.358"></a>
<span class="sourceLineNo">359</span>   * @param iterator the iterator to copy<a name="line.359"></a>
<span class="sourceLineNo">360</span>   * @param type the type of the elements<a name="line.360"></a>
<span class="sourceLineNo">361</span>   * @return a newly-allocated array into which all the elements of the iterator<a name="line.361"></a>
<span class="sourceLineNo">362</span>   *         have been copied<a name="line.362"></a>
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<span class="sourceLineNo">365</span>  public static &lt;T&gt; T[] toArray(<a name="line.365"></a>
<span class="sourceLineNo">366</span>      Iterator&lt;? extends T&gt; iterator, Class&lt;T&gt; type) {<a name="line.366"></a>
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<span class="sourceLineNo">371</span>  /**<a name="line.371"></a>
<span class="sourceLineNo">372</span>   * Adds all elements in {@code iterator} to {@code collection}. The iterator<a name="line.372"></a>
<span class="sourceLineNo">373</span>   * will be left exhausted: its {@code hasNext()} method will return<a name="line.373"></a>
<span class="sourceLineNo">374</span>   * {@code false}.<a name="line.374"></a>
<span class="sourceLineNo">375</span>   *<a name="line.375"></a>
<span class="sourceLineNo">376</span>   * @return {@code true} if {@code collection} was modified as a result of this<a name="line.376"></a>
<span class="sourceLineNo">377</span>   *         operation<a name="line.377"></a>
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<span class="sourceLineNo">389</span>  /**<a name="line.389"></a>
<span class="sourceLineNo">390</span>   * Returns the number of elements in the specified iterator that equal the<a name="line.390"></a>
<span class="sourceLineNo">391</span>   * specified object. The iterator will be left exhausted: its<a name="line.391"></a>
<span class="sourceLineNo">392</span>   * {@code hasNext()} method will return {@code false}.<a name="line.392"></a>
<span class="sourceLineNo">393</span>   *<a name="line.393"></a>
<span class="sourceLineNo">394</span>   * @see Collections#frequency<a name="line.394"></a>
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<span class="sourceLineNo">415</span>   * Returns an iterator that cycles indefinitely over the elements of {@code<a name="line.415"></a>
<span class="sourceLineNo">416</span>   * iterable}.<a name="line.416"></a>
<span class="sourceLineNo">417</span>   *<a name="line.417"></a>
<span class="sourceLineNo">418</span>   * &lt;p&gt;The returned iterator supports {@code remove()} if the provided iterator<a name="line.418"></a>
<span class="sourceLineNo">419</span>   * does. After {@code remove()} is called, subsequent cycles omit the removed<a name="line.419"></a>
<span class="sourceLineNo">420</span>   * element, which is no longer in {@code iterable}. The iterator's<a name="line.420"></a>
<span class="sourceLineNo">421</span>   * {@code hasNext()} method returns {@code true} until {@code iterable} is<a name="line.421"></a>
<span class="sourceLineNo">422</span>   * empty.<a name="line.422"></a>
<span class="sourceLineNo">423</span>   *<a name="line.423"></a>
<span class="sourceLineNo">424</span>   * &lt;p&gt;&lt;b&gt;Warning:&lt;/b&gt; Typical uses of the resulting iterator may produce an<a name="line.424"></a>
<span class="sourceLineNo">425</span>   * infinite loop. You should use an explicit {@code break} or be certain that<a name="line.425"></a>
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<span class="sourceLineNo">460</span>   * Returns an iterator that cycles indefinitely over the provided elements.<a name="line.460"></a>
<span class="sourceLineNo">461</span>   *<a name="line.461"></a>
<span class="sourceLineNo">462</span>   * &lt;p&gt;The returned iterator supports {@code remove()} if the provided iterator<a name="line.462"></a>
<span class="sourceLineNo">463</span>   * does. After {@code remove()} is called, subsequent cycles omit the removed<a name="line.463"></a>
<span class="sourceLineNo">464</span>   * element, but {@code elements} does not change. The iterator's<a name="line.464"></a>
<span class="sourceLineNo">465</span>   * {@code hasNext()} method returns {@code true} until all of the original<a name="line.465"></a>
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<span class="sourceLineNo">467</span>   *<a name="line.467"></a>
<span class="sourceLineNo">468</span>   * &lt;p&gt;&lt;b&gt;Warning:&lt;/b&gt; Typical uses of the resulting iterator may produce an<a name="line.468"></a>
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<span class="sourceLineNo">470</span>   * you will eventually remove all the elements.<a name="line.470"></a>
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<span class="sourceLineNo">475</span><a name="line.475"></a>
<span class="sourceLineNo">476</span>  /**<a name="line.476"></a>
<span class="sourceLineNo">477</span>   * Combines two iterators into a single iterator. The returned iterator<a name="line.477"></a>
<span class="sourceLineNo">478</span>   * iterates across the elements in {@code a}, followed by the elements in<a name="line.478"></a>
<span class="sourceLineNo">479</span>   * {@code b}. The source iterators are not polled until necessary.<a name="line.479"></a>
<span class="sourceLineNo">480</span>   *<a name="line.480"></a>
<span class="sourceLineNo">481</span>   * &lt;p&gt;The returned iterator supports {@code remove()} when the corresponding<a name="line.481"></a>
<span class="sourceLineNo">482</span>   * input iterator supports it.<a name="line.482"></a>
<span class="sourceLineNo">483</span>   *<a name="line.483"></a>
<span class="sourceLineNo">484</span>   * &lt;p&gt;&lt;b&gt;Note:&lt;/b&gt; the current implementation is not suitable for nested<a name="line.484"></a>
<span class="sourceLineNo">485</span>   * concatenated iterators, i.e. the following should be avoided when in a loop:<a name="line.485"></a>
<span class="sourceLineNo">486</span>   * {@code iterator = Iterators.concat(iterator, suffix);}, since iteration over the<a name="line.486"></a>
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<span class="sourceLineNo">499</span>   * iterates across the elements in {@code a}, followed by the elements in<a name="line.499"></a>
<span class="sourceLineNo">500</span>   * {@code b}, followed by the elements in {@code c}. The source iterators<a name="line.500"></a>
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<span class="sourceLineNo">502</span>   *<a name="line.502"></a>
<span class="sourceLineNo">503</span>   * &lt;p&gt;The returned iterator supports {@code remove()} when the corresponding<a name="line.503"></a>
<span class="sourceLineNo">504</span>   * input iterator supports it.<a name="line.504"></a>
<span class="sourceLineNo">505</span>   *<a name="line.505"></a>
<span class="sourceLineNo">506</span>   * &lt;p&gt;&lt;b&gt;Note:&lt;/b&gt; the current implementation is not suitable for nested<a name="line.506"></a>
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<span class="sourceLineNo">516</span>    checkNotNull(c);<a name="line.516"></a>
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<span class="sourceLineNo">522</span>   * iterates across the elements in {@code a}, followed by the elements in<a name="line.522"></a>
<span class="sourceLineNo">523</span>   * {@code b}, followed by the elements in {@code c}, followed by the elements<a name="line.523"></a>
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<span class="sourceLineNo">526</span>   * &lt;p&gt;The returned iterator supports {@code remove()} when the corresponding<a name="line.526"></a>
<span class="sourceLineNo">527</span>   * input iterator supports it.<a name="line.527"></a>
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<span class="sourceLineNo">530</span>   * concatenated iterators, i.e. the following should be avoided when in a loop:<a name="line.530"></a>
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<span class="sourceLineNo">547</span>   * iterates across the elements of each iterator in {@code inputs}. The input<a name="line.547"></a>
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<span class="sourceLineNo">551</span>   * input iterator supports it.<a name="line.551"></a>
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<span class="sourceLineNo">554</span>   * concatenated iterators, i.e. the following should be avoided when in a loop:<a name="line.554"></a>
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<span class="sourceLineNo">574</span>   * concatenated iterators, i.e. the following should be avoided when in a loop:<a name="line.574"></a>
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<span class="sourceLineNo">593</span>        // the first NPE, and the next time around we'll call inputs.next()<a name="line.593"></a>
<span class="sourceLineNo">594</span>        // again, incorrectly moving beyond the error.<a name="line.594"></a>
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<span class="sourceLineNo">620</span>   * Divides an iterator into unmodifiable sublists of the given size (the final<a name="line.620"></a>
<span class="sourceLineNo">621</span>   * list may be smaller). For example, partitioning an iterator containing<a name="line.621"></a>
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<span class="sourceLineNo">625</span>   *<a name="line.625"></a>
<span class="sourceLineNo">626</span>   * &lt;p&gt;The returned lists implement {@link java.util.RandomAccess}.<a name="line.626"></a>
<span class="sourceLineNo">627</span>   *<a name="line.627"></a>
<span class="sourceLineNo">628</span>   * @param iterator the iterator to return a partitioned view of<a name="line.628"></a>
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<span class="sourceLineNo">640</span>   * Divides an iterator into unmodifiable sublists of the given size, padding<a name="line.640"></a>
<span class="sourceLineNo">641</span>   * the final iterator with null values if necessary. For example, partitioning<a name="line.641"></a>
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<span class="sourceLineNo">645</span>   *<a name="line.645"></a>
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<span class="sourceLineNo">647</span>   *<a name="line.647"></a>
<span class="sourceLineNo">648</span>   * @param iterator the iterator to return a partitioned view of<a name="line.648"></a>
<span class="sourceLineNo">649</span>   * @param size the desired size of each partition<a name="line.649"></a>
<span class="sourceLineNo">650</span>   * @return an iterator of immutable lists containing the elements of {@code<a name="line.650"></a>
<span class="sourceLineNo">651</span>   *     iterator} divided into partitions (the final iterable may have<a name="line.651"></a>
<span class="sourceLineNo">652</span>   *     trailing null elements)<a name="line.652"></a>
<span class="sourceLineNo">653</span>   * @throws IllegalArgumentException if {@code size} is nonpositive<a name="line.653"></a>
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<span class="sourceLineNo">712</span>   * Returns all instances of class {@code type} in {@code unfiltered}. The<a name="line.712"></a>
<span class="sourceLineNo">713</span>   * returned iterator has elements whose class is {@code type} or a subclass of<a name="line.713"></a>
<span class="sourceLineNo">714</span>   * {@code type}.<a name="line.714"></a>
<span class="sourceLineNo">715</span>   *<a name="line.715"></a>
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<span class="sourceLineNo">1219</span>    @Override<a name="line.1219"></a>
<span class="sourceLineNo">1220</span>    public E next() {<a name="line.1220"></a>
<span class="sourceLineNo">1221</span>      if (!hasPeeked) {<a name="line.1221"></a>
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<span class="sourceLineNo">1236</span>    @Override<a name="line.1236"></a>
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<span class="sourceLineNo">1246</span>  /**<a name="line.1246"></a>
<span class="sourceLineNo">1247</span>   * Returns a {@code PeekingIterator} backed by the given iterator.<a name="line.1247"></a>
<span class="sourceLineNo">1248</span>   *<a name="line.1248"></a>
<span class="sourceLineNo">1249</span>   * &lt;p&gt;Calls to the {@code peek} method with no intervening calls to {@code<a name="line.1249"></a>
<span class="sourceLineNo">1250</span>   * next} do not affect the iteration, and hence return the same object each<a name="line.1250"></a>
<span class="sourceLineNo">1251</span>   * time. A subsequent call to {@code next} is guaranteed to return the same<a name="line.1251"></a>
<span class="sourceLineNo">1252</span>   * object again. For example: &lt;pre&gt;   {@code<a name="line.1252"></a>
<span class="sourceLineNo">1253</span>   *<a name="line.1253"></a>
<span class="sourceLineNo">1254</span>   *   PeekingIterator&lt;String&gt; peekingIterator =<a name="line.1254"></a>
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<span class="sourceLineNo">1258</span>   *   String a3 = peekingIterator.next(); // also returns "a"}&lt;/pre&gt;<a name="line.1258"></a>
<span class="sourceLineNo">1259</span>   *<a name="line.1259"></a>
<span class="sourceLineNo">1260</span>   * Any structural changes to the underlying iteration (aside from those<a name="line.1260"></a>
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<span class="sourceLineNo">1262</span>   * will leave the iterator in an undefined state.<a name="line.1262"></a>
<span class="sourceLineNo">1263</span>   *<a name="line.1263"></a>
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<span class="sourceLineNo">1266</span>   *<a name="line.1266"></a>
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<span class="sourceLineNo">1268</span>   * it &lt;i&gt;might&lt;/i&gt; be returned to the caller, although this is neither<a name="line.1268"></a>
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<span class="sourceLineNo">1271</span>   * {@code PeekingIterator} when the behavior of the implementation is<a name="line.1271"></a>
<span class="sourceLineNo">1272</span>   * known to meet the contract guaranteed by this method.<a name="line.1272"></a>
<span class="sourceLineNo">1273</span>   *<a name="line.1273"></a>
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<span class="sourceLineNo">1280</span>   * @return a peeking iterator backed by that iterator. Apart from the<a name="line.1280"></a>
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<span class="sourceLineNo">1297</span>   * Simply returns its argument.<a name="line.1297"></a>
<span class="sourceLineNo">1298</span>   *<a name="line.1298"></a>
<span class="sourceLineNo">1299</span>   * @deprecated no need to use this<a name="line.1299"></a>
<span class="sourceLineNo">1300</span>   * @since 10.0<a name="line.1300"></a>
<span class="sourceLineNo">1301</span>   */<a name="line.1301"></a>
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<span class="sourceLineNo">1307</span>  /**<a name="line.1307"></a>
<span class="sourceLineNo">1308</span>   * Returns an iterator over the merged contents of all given<a name="line.1308"></a>
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<span class="sourceLineNo">1310</span>   * Equivalent entries will not be de-duplicated.<a name="line.1310"></a>
<span class="sourceLineNo">1311</span>   *<a name="line.1311"></a>
<span class="sourceLineNo">1312</span>   * &lt;p&gt;Callers must ensure that the source {@code iterators} are in<a name="line.1312"></a>
<span class="sourceLineNo">1313</span>   * non-descending order as this method does not sort its input.<a name="line.1313"></a>
<span class="sourceLineNo">1314</span>   *<a name="line.1314"></a>
<span class="sourceLineNo">1315</span>   * &lt;p&gt;For any equivalent elements across all {@code iterators}, it is<a name="line.1315"></a>
<span class="sourceLineNo">1316</span>   * undefined which element is returned first.<a name="line.1316"></a>
<span class="sourceLineNo">1317</span>   *<a name="line.1317"></a>
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<span class="sourceLineNo">1321</span>  public static &lt;T&gt; UnmodifiableIterator&lt;T&gt; mergeSorted(<a name="line.1321"></a>
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<span class="sourceLineNo">1325</span>    checkNotNull(comparator, "comparator");<a name="line.1325"></a>
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<span class="sourceLineNo">1330</span>  /**<a name="line.1330"></a>
<span class="sourceLineNo">1331</span>   * An iterator that performs a lazy N-way merge, calculating the next value<a name="line.1331"></a>
<span class="sourceLineNo">1332</span>   * each time the iterator is polled. This amortizes the sorting cost over the<a name="line.1332"></a>
<span class="sourceLineNo">1333</span>   * iteration and requires less memory than sorting all elements at once.<a name="line.1333"></a>
<span class="sourceLineNo">1334</span>   *<a name="line.1334"></a>
<span class="sourceLineNo">1335</span>   * &lt;p&gt;Retrieving a single element takes approximately O(log(M)) time, where M<a name="line.1335"></a>
<span class="sourceLineNo">1336</span>   * is the number of iterators. (Retrieving all elements takes approximately<a name="line.1336"></a>
<span class="sourceLineNo">1337</span>   * O(N*log(M)) time, where N is the total number of elements.)<a name="line.1337"></a>
<span class="sourceLineNo">1338</span>   */<a name="line.1338"></a>
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<span class="sourceLineNo">1341</span>    final Comparator&lt;? super T&gt; comparator;<a name="line.1341"></a>
<span class="sourceLineNo">1342</span><a name="line.1342"></a>
<span class="sourceLineNo">1343</span>    public MergingIterator(Iterable&lt;? extends Iterator&lt;? extends T&gt;&gt; iterators,<a name="line.1343"></a>
<span class="sourceLineNo">1344</span>        Comparator&lt;? super T&gt; itemComparator) {<a name="line.1344"></a>
<span class="sourceLineNo">1345</span>      this.comparator = itemComparator;<a name="line.1345"></a>
<span class="sourceLineNo">1346</span><a name="line.1346"></a>
<span class="sourceLineNo">1347</span>      // A comparator that's used by the heap, allowing the heap<a name="line.1347"></a>
<span class="sourceLineNo">1348</span>      // to be sorted based on the top of each iterator.<a name="line.1348"></a>
<span class="sourceLineNo">1349</span>      Comparator&lt;PeekingIterator&lt;T&gt;&gt; heapComparator =<a name="line.1349"></a>
<span class="sourceLineNo">1350</span>          new Comparator&lt;PeekingIterator&lt;T&gt;&gt;() {<a name="line.1350"></a>
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<span class="sourceLineNo">1352</span>            public int compare(PeekingIterator&lt;T&gt; o1, PeekingIterator&lt;T&gt; o2) {<a name="line.1352"></a>
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<span class="sourceLineNo">1355</span>          };<a name="line.1355"></a>
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<span class="sourceLineNo">1357</span>      queue = new PriorityQueue&lt;PeekingIterator&lt;T&gt;&gt;(2, heapComparator);<a name="line.1357"></a>
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<span class="sourceLineNo">1359</span>      for (Iterator&lt;? extends T&gt; iterator : iterators) {<a name="line.1359"></a>
<span class="sourceLineNo">1360</span>        if (iterator.hasNext()) {<a name="line.1360"></a>
<span class="sourceLineNo">1361</span>          queue.add(Iterators.peekingIterator(iterator));<a name="line.1361"></a>
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<span class="sourceLineNo">1366</span>    @Override<a name="line.1366"></a>
<span class="sourceLineNo">1367</span>    protected T computeNext() {<a name="line.1367"></a>
<span class="sourceLineNo">1368</span>      if (queue.isEmpty()) {<a name="line.1368"></a>
<span class="sourceLineNo">1369</span>        return endOfData();<a name="line.1369"></a>
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<span class="sourceLineNo">1371</span><a name="line.1371"></a>
<span class="sourceLineNo">1372</span>      PeekingIterator&lt;T&gt; nextIter = queue.poll();<a name="line.1372"></a>
<span class="sourceLineNo">1373</span>      T next = nextIter.next();<a name="line.1373"></a>
<span class="sourceLineNo">1374</span><a name="line.1374"></a>
<span class="sourceLineNo">1375</span>      if (nextIter.hasNext()) {<a name="line.1375"></a>
<span class="sourceLineNo">1376</span>        queue.add(nextIter);<a name="line.1376"></a>
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<span class="sourceLineNo">1378</span><a name="line.1378"></a>
<span class="sourceLineNo">1379</span>      return next;<a name="line.1379"></a>
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<span class="sourceLineNo">1382</span><a name="line.1382"></a>
<span class="sourceLineNo">1383</span>  /**<a name="line.1383"></a>
<span class="sourceLineNo">1384</span>   * Precondition tester for {@code Iterator.remove()} that throws an exception with a consistent<a name="line.1384"></a>
<span class="sourceLineNo">1385</span>   * error message.<a name="line.1385"></a>
<span class="sourceLineNo">1386</span>   */<a name="line.1386"></a>
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<span class="sourceLineNo">1388</span>    checkState(canRemove, "no calls to next() since the last call to remove()");<a name="line.1388"></a>
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<span class="sourceLineNo">1390</span><a name="line.1390"></a>
<span class="sourceLineNo">1391</span>  /**<a name="line.1391"></a>
<span class="sourceLineNo">1392</span>   * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557<a name="line.1392"></a>
<span class="sourceLineNo">1393</span>   */<a name="line.1393"></a>
<span class="sourceLineNo">1394</span>  static &lt;T&gt; ListIterator&lt;T&gt; cast(Iterator&lt;T&gt; iterator) {<a name="line.1394"></a>
<span class="sourceLineNo">1395</span>    return (ListIterator&lt;T&gt;) iterator;<a name="line.1395"></a>
<span class="sourceLineNo">1396</span>  }<a name="line.1396"></a>
<span class="sourceLineNo">1397</span>}<a name="line.1397"></a>




























































</pre>
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